The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
Aspects of the present invention relate to a fluidized bed reactor and a process for the production of granules, such as granules of urea or ammonium nitrate, typically used as a fertilizer material.
To reduce agglomeration problems during storage of urea granules, the water content in the final granules should be low, for instance below 0.25% by total weight of the granules.
To produce drier granules the residence time in the granulator can be increased, e.g., by using higher bed levels. However, this requires higher pressures of the fluidization air and, consequently, more power consumption.
Alternatively, the water content can be reduced by atomizing the urea solution to finer droplets. This requires more air to atomize the urea solution and, consequently, more power consumption.
Lower water contents of the final granules can also be achieved by spraying a more concentrated urea solution. EP-A 0 289 074, for instance, teaches to use a solution with a urea content of 70-99.9 wt %. However, the use of low water content urea concentrates reduces the cooling effect of water evaporation. To compensate for this, cooling by air should be increased by higher flow speeds of the air used for fluidization. Consequently, also this option results in higher energy consumption.
A fluidized bed granulator and a process resulting in dry granules without requiring high energy consumption can be beneficial.